maledicti sunt in fluvio
by neonmarshie
Summary: Most people tend to stay human their whole life, as that is the wide expectation that society has. However, a mystical river settled in the deep green forests of Gravity Falls threatens to change all of that, starting with a young boy named Dipper Pines. Monster Falls AU.
1. Chapter 1

_;cursed river_

 _The Fluvius Cantatis-a true mystery to anyone who has ever happened to set their eyes upon it. With it's abnormal but captivating lavender stones and shimmering, unnaturally clear water, it is quite the sight to behold._

 _Unfortunately, I have never had the opportunity to study this rather odd body of water, but would like to in the future._

Dipper Pines groaned as he reached into his navy blue vest's pocket and-to his dismay- he had left his blacklight on his bed. He had planned to help his Great-Uncle Stanford, who was the original author of all three journals, research on a topic that it seemed his uncle had forgotten about a long time ago. However, Dipper didn't have the blacklight, which would allow him to see Stanford's hidden messages, revealing the river's true threat.

The boy supposed he could've just asked Ford about the river, but that probably would have lead him into a conversation about not going. "Well, that's it for that," Dipper mumbled, attempting to pick up his blue gel pen but accidentally sending it rolling towards the river. "My pen!" Dipper yelped, running towards it desperately.

Little did he know, a familiar presence had been watching him the entire time.

Bill Cipher, all powerful dream demon was in the mindscape, watching the young boy from afar. The demon chuckled as he watched Dipper inch over to the river, the Fluvius Cantatis, hesitantly. Bill wished that the kid's clumsiness would work in his favour once again. Unfortunately, the boy was not touching the cursed body of water anytime soon. This is where the triangular demon would intervene.

Bill hovered midair, hands resting against the back of his triangular body as he slowly guided Dipper's blue gel pen towards the river. He chuckled lively when thinking of the boy setting his eyes upon the mutated, ugly creature he would morph into after making contact with the Fluvius. He rolled his eye as he realized Dipper was too interested in Sixer's 'research' to notice his pen inching towards the gentle water. "Hey Pine Tree, your pen's-"

"My pen!"

The demon chuckled again as he watched the boy yelp in distress as he realized his pen was in the midst of rolling into the river. Bill clapped, gliding closer to the boy to admire his work.

"Ugh, seriously?" Dipper moaned, grabbing his pen out of the water. Curious, he looked around. It wasn't windy outside; the trees were barely moving, so why did that happen? He started to make his way back to the Shack, but stopped when he realized that he had left his journal on the riverbank.

Sighing, he went to grab it. Dipper kneeled down, finding himself staring at the river, entranced by it's strange beauty.

Bill groaned, looking at the boy. He hadn't fallen in the water yet, even with his genius pen plan. The demon perked up. He had just enough energy left for interacting with physical objects, so why not use it on this?

Dipper's eyes perked up as he felt the air shift, like an extra presence had entered the area he was in. Cautiously, he looked behind him, only to find just dead air. Dipper huffed, reassuring himself. "Ok, chill out. No one's here but you." Turning back around, he went to pick up the journal-

Dipper screamed as he was shoved into the water. "I can't-can't swim!" The boy yelled, shivering in the freezing cold river.

The dream demon, still inside the mindscape, was guffawing, watching the boy flail his arms around, still screaming wildly. "AHAHAHAHAH!" He chortled, unable to stop himself. "YOU DON'T KNOW IT YET, KID, BUT YOU'RE SUCH A RIOT!" He remarked, still laughing. Dipper's arms were flopping around wildly, coming dangerously close to the spot where Bill was hovering. But the demon didn't seem to notice. Right up until Dipper's hand latched onto one of Bill's black, skinny, boneless legs, dragging the demon into the water with him.

Bill screamed as he was dunked into the cursed river. "NO! YOU IDIOT KID! DO YOU REALIZE WHAT YOU'VE DONE!" Bill's single eye widened as he was pulled deeper into the waters of the Fluvius Cantatis. He shuddered. The dream demon could practically feel the curse dissolving into his one dimensional body. The one that would soon be robbed of him, all because of one insanely ignorant kid. He couldn't be sure, however, that the river could work backwards. Many of the supernatural creatures in the forest had made contact and remained unchanged. Bill hoped that would be the case for him.

Dipper gasped for air as he broke through the water's surface, relieved that he had gotten out of there alive. The boy coughed, resting his head on the river bank. "Why...ugh...I...hate...water," Dipper complained, gasping after each word. He moaned, not realizing the world's colours shift to black and white as Bill projected himself into his brain.

"THANKS A LOT, PINE TREE!" Bill announced sarcastically, a slight hostile tone creeping into his voice.

Dipper's head snapped up when he heard the demon speak. "B-b-Bill?" The boy stammered, standing up, turning around and coming face to eye with a giant yellow triangle. Dipper clenched his fists, remembering the past two major incidents that the demon had caused. "I don't want anything to do with you," he hardened, walking over to the spot he had placed the journal. "And you are  
 _not_ getting this!" Dipper exclaimed, hugging the maroon book protectively.

Bill laughed dryly. "CUTE, PINE TREE, ADORABLE." The demon's aura suddenly shifted, tension rising. "YOU KNOW, I WANTED TO HELP YOU WITH THIS!"

Dipper furrowed his brows, confused. "What? What are you saying?" The demon had never seemed to want to help him before. Realizing what was going on, Dipper rolled his soft brown eyes. "I'm not making another deal with you, Bill! Don't think I forget t what happened the last time!"

Bill started chortling again, leaving Dipper very uncomfortable. The demon's laughter made him feel like he was being ridiculed. "GREAT JOB PINE TREE! ONCE AGAIN YOU ARE ONE HUNDRED PERCENT WRONG ABOUT EVERYTHING!" The demon pulled out a white mug filled with a murky red substance. "HAVE A CUP OF TEA!" He exclaimed, shoving it into the boy's hand. "THAT'S HUMAN BLOOD BY THE WAY."

Dipper yelped, throwing the mug onto the ground and watching it fade from existence right before contact. The boy growled and pointed at the demon in front of him, who was managing to look smug without a mouth. "I-I don't know what the heck you want out of me, but I am not giving in!" He thought for a moment. "So just-just give it up already man!"

Bill sat on the log behind Dipper, shocking the twelve year old in front of him. He crossed his legs, raising his single brow. "YOU KNOW, I LIKED YOU!" Bill chuckled. "YOU WERE A GREAT PUPPET, MADE MY JOB EASY!" The demon glared at the boy. "BUT YOU BETTER HOPE THAT WHAT YOU JUST DID DOESN'T EFFECT ME, PINE TREE!"

Dipper furrowed his brows, backing away from the demon. "W-what? What are you-"

"AHAHAHAHAHAH!" Bill chuckled, appearing on the other side of Dipper, scaring him out of his wits. "YOU DON'T KNOW?" Dipper bit his lip, confused and frightened. "THIS RIVER HAS MAGICAL PROPERTIES!"

Dipper gasped, hoping Bill would feed him more information. "What kind of magical properties?"

Bill laughed. "YOU REALLY THINK I'M GOING TO TELL YOU?" Dipper looked very confused now. "GOOD LUCK WITH WHAT'S COMING, KID!" Bill floated upwards, disappearing into a strange white light. "YOU BETTER HOPE I'M NOT ON YOUR DOORSTEP BY TOMORROW NIGHT!" The demon's voice echoed, then fading away, leaving only the deafening sound of rushing water.

Dipper sunk down onto the ground, shivering. "W-what _was_ that?" He wondered aloud, staring into space. _On your doorstep by tomorrow night?_  
What was Bill talking about? What was he going to do to him? The boy sighed, standing up and picking his journal off of the ground. He would go home, put on some dry clothes, and try not to think about it.

"Ugghh," Dipper moaned, flinging himself onto the yellow couch in the living room of the Mystery Shack. He had changed his clothes, but his hair was still wet. That wasn't his only problem, however. There was a persistent ache in his lower legs, feeling oddly similar to growing pains. Dipper hoped he was getting taller. Most of the boys in his class were at least five foot three and above, but he had been stuck under four feet for years. Not only that it would give him a better chance with Wendy.

"Hey kid," Stan grumbled, walking into the living room, clad in only his stained white undershirt and striped blue underpants, a Pitt Cola in his hand. "What're you watching?"

Dipper sighed, resting his cheek on his fist. He did not feel like talking. "Nothing, just thinking."

Stan chuckled. "Ahh, like always." The old man began to walk away, but noticed Dipper's still-sopping wet hair. He knew that the kid would never take a bath out of his own free will, so what was all this about? "What's with the wet hair?"

"Would you buy taking a shower?" Dipper asked, rubbing the back of his neck awkwardly.

Rolling his eyes, Stan shook his head. "I've spent time in prison, kid. I basically have a built in lie detector." He took a swig of his Pitt Cola. "Gimme the goods!"

The boy in the chair huffed, having to give the answer now. "Fine. I-" Dipper took a breath, preparing to be ridiculed. "I kind of fell in a river?"

Stan raised his brows. "Yeesh!" He chuckled, leaning on the yellow chair. "Tough luck ya' got there!" Stan thought for a minute, an idea taking place in his head. "Was the water drinking water clean?"

Dipper furrowed his brows. "Uh, I dunno." The boy frowned, confused. "W-why are you asking me this, Grunkle Stan?"

Stan stood up straight, a gleeful look on his face. "This is perfect!" He exclaimed, throwing his hands up in the air. "I've been trying to think up a hot new attraction for weeks!" The grey-haired man cleared his throat. "I can see it now: Mr. Mystery's Mystical Water! It'll be perfect!" Stan announced, walking out of the living room, towards the kitchen.

The boy on the couch was busy trying to put his uncle's sentences together. He soon remembered Bill's warning about the river Fluvius. "Wait, you're gonna sell it?" Rapidly Dipper jumped off of the couch and ran towards Stan. "No, no, no Grunkle Stan you have no idea  
 _how_ bad an idea that is!"

Unbeknownst to the river's true origins, Stan just rolled his eyes. "Geez, what's gonna happen? Am I gonna get in trouble with the food cops or something?" The man chuckled, laughing at his own joke.

"That river is cursed, Stan!" Dipper exclaimed, pulling out Ford's third journal and flipping the page to the one about the Fluvius. "I-I don't know how, but it is!" He mentioned, holding out the journal for his uncle to see.

Stan huffed, sick of the conspiracies. "Listen, I'm sure whatever my brother said in that dumb journal you can just ignore." The elderly man threw his Pitt Cola into the trash, walking out of the room. "And besides, how terrible can this curse be?"

Dipper walked after his uncle, wincing at the pains in his legs. "But Grunkle-"

"No buts. You're showing us where that river is tomorrow, no matter what happens, you hear me kid?"

"Grunkle-" Dipper stopped as his great-uncle glared at him, his message very well said through his eyes. "Fine. I'll show you." The boy walked past his uncle, heading back into his attic bedroom. "Just don't complain to me when you turn yourself into a sandwich."

And with that Dipper disappeared up the stairs, wincing with every step, the pains in his legs becoming worse by the minute.


	2. Chapter 21

Dipper sighed, kicking an absent stone as he read the map to the Fluvius Cantatis from Ford's journal, helping Stan, Mabel, Wendy, and Soos find their way to it. The boy had attempted to once again get his point across to Stan, but it hadn't worked.

 _"Grunkle Stan, for the millionth time, the river is-"_

 _"Cursed, yada yada yada, I've heard it all before, kid." The grey-haired nan kneeled down to face his nephew, putting a hand to his shoulder. "Listen, if you keep spitting all this nonsense, I'll be taking that journal and giving my brother a talk. He can't keep putting all this paranormal shi-stuff into your head."_

 _Dipper groaned, putting a hand to his head. "But it's not just-just stuff, Grunkle Stan! Ask Ford! He'll tell you!"_

 _Stan rolled his eyes. "As if. Stanford could care less." The man stood up, placing his fez on his head. "And don't you think about going down there." Stan thought for a moment. "Go tell your sister to pack a bag. We'll be heading out to that river as soon as Wendy and Soos get here."_

 _The preteen stood in silence as Stan walked by him, out into the gift shop. Groaning, Dipper pushed open the door, following his great-uncle. "I'm just trying to warn you guys! Ever since I-uh, fell in, I've been feeling weird," Dipper explained, catching his uncle's attention._

 _Stan stared for a moment, but then sighed, setting the box filled with water bottles down on the counter which held the cash register. "Alright, kid. I don't want to hear one more word about whatever stupid thing you read in my brother's dumb journal!" Stan threatened, getting angry, more at Ford than the boy in front of him. "Now go_  
style="font-size: 16pt;"do what I said _and get your sister!"_

 _Dipper balled his fists, walking back through the door and storming up the stairs. Why would no one listen?_

So here he was, legs aching with every step, leading his family and friends to a cursed river that could potentially harm them terribly. Well, it was their faults if it did. The only person who had listened to him at all had been Mabel, who had only took it all too lightly and turned the whole thing into a big joke.

The five of them walked for what seemed like hours, until they finally came up upon the very same clearing Dipper had been at a day earlier, the one with the crystal clear river running through it.

Mabel gasped with glee, her eyes lighting up. "Wow! It's beautiful!" The girl gushed, running towards it. She was right, it truly was. The area around the Fluvius was a glittering blue, with unnaturally perfect toadstools and daisies surrounding it's riverbank. The trees around it seemed to touch the sky, with leaves that looked almost purple. The Fluvius Cantatis had a small waterfall on it's right side, and crystal clear water was trickling down from it, filtering into the main area of he pool. The water had a strange blue aura to it, which was only accompanied by the strange lavender glow from the purple stones at the bottom.

Dipper cringed as he watched his sister reach into the water-the cursed water- and grab a purple stone. After coming here the day before, planning to only take samples to bring back to Ford, and falling in, he hadn't planned on coming back. What if being near the water only amplified the curse? What if Bill came back? All the questions were more than he'd wanted to have.

"Dipper, dude, you okay?" The boy unfroze from his trance as he heard a familiar teenage voice from behind him. _Wendy_.

The preteen sighed. "Yeah, I guess," Dipper huffed, sitting on a rotting log, watching Stan disperse water bottles to Mabel and Soos, who were eager to begin their task. "I juts have a really bad headache and my legs hurt a lot and I'm really itchy," the boy explained, scratching at a spot on his arm.

Wendy furrowed her brows, putting a hand to Dipper's forehead. "Dude, you're really hot."

Dipper blushed, knowing what the girl meant but thinking of it as another way. "I-uh-Maybe it's just sweat?" He stammered, feeling awkward.

"Nah, Dip, this is like, abnormally hot," Wendy explained, concerned for the boy in front of her. "Do you think you're getting the flu?"

Dipper sighed. If that was all this was then he would be relieved. "I don't know," he mumbled, staring out at the river. "I haven't really been feeling very well, so probably."

The redhead beside him smiled slightly. "Do ya' wanna tell Stan? I'm sure he'd let you go back to the Shack."

Dipper chuckled awkwardly. "I dunno about that," he muttered. Stan was pretty serious about this whole water bottle thing, and if he let the boy go home it would be nearly a miracle.

"Wendy, stop sitting around and get to work! You too kid!" Stan yelled at the two of them, taking a swig of a water bottle Soos had recently filled.

Wendy sighed, patting Dipper on the back. "Good luck Dipper." She got up, walking towards Stanley. The old man handed her a water bottle, and she sat down beside Mabel, filling it up.

Stan walked over to Dipper, who was still sitting on the log. He had a gruff look on his face, which didn't mean good things for the boy. "Corduroy told me you've got a fever," Stan mentioned, slapping his hand to Dipper's forehead. His eyes widened. "Geez, kid! No wonder you can't shut up about magic and curses! With a temperature like this you're probably half-delirious!"

"Grunkle Stan-"

"No buts. I don't wanna do this, but go home. Sit in your bed. Get some rest. Whatever. I don't care. Just get out of here, I don't want this water contaminated."

Dipper stood up, grabbing his backpack-and the journal. Perfect. He could take the time to study the river and possibly even ask Great-Uncle Ford about it. He looked at the river. Wendy was facing his way and winked at him. Dipper winked back, mouthing the word 'thanks.' The teenager grinned back, going back to her work as she watched Dipper make his way back to the Shack.

"And don't get used to it, kid! We'll be back here in the morning! Get prepared to work!"

Dipper sat in the living room, once again reading over Ford's passage about the Fluvius. This time he held the blacklight over it, but it held no other secrets. The page simply ended with a phrase that read: 'multiple forest creatures I am on good terms with warned me about this river, so I decided to leave it alone.'

The boy sighed, grabbing the remote and switching the television on for background noise. One of Stan's weird old black and white movies flashed on. Dipper changed it to the 'Used To Be About History Channel,' so he wouldn't have to hear the annoying voices of probably dead people.

Dipper stared at the illustration of the river. Was it even the same one? Was he just being paranoid like always? The boy bit his lip, contemplating on telling his great-uncle about all this. Maybe Ford could create an antidote to combat whatever the curse was before it took its hold? The brunet closed the third journal, prepared to converse with Ford about it.

Dipper walked slowly into the gift shop, wincing at the straining pains in his legs. These couldn't be something as simple as growing pains. These certainly had to be part of the curse right? Quickly, Dipper punched the code into the vending machine. He watched with apprehension as the door swung open, kicking up a considerable amount of dust. Should he do this? Would Great-Uncle Ford be angry with him for going to the river in the first place? They were all thoughts to consider. He didn't want Stanford to be angry with him, and he sure wouldn't tell his uncle about Stan's selling of the mystical water.

Dipper stepped into the elevator. Oh well. All he was worrying about was the curse that would soon impact him. And that was all that mattered right now.

Bill Cipher had asked everyone he knew who specialized in curses about the Fluvius, and absolutely none of them had even heard of the damned thing before. He ended up imprisoning every last one of them and planned to torture them daily. He figured that would squeeze the answer out of them.

So here the grand demon himself was, sitting on his throne and staring hopelessly at his image in a handheld mirror. All because of Pine Tree everything would be robbed of him. His powers, his Nightmare Realm, his triangular form... everything. And without his powers, Bill was a nub with a psychopathic, sadistic personality. The demon sighed, poofing the mirror away and creating a flame. He stared mindlessly at the magnificent cyan colour.

Bill shot out of his seat, yelling in rage, becoming blood red and his cyan flame transforming to a bright orange, engulfing the demon. "PINE TREE!" He screamed angrily, using magic to throw all of his room's possessions onto a wall on the back side of the room. Bill hovered silently as he heard the crashes of the items hitting the wall as his body slowly faded back to yellow.

Then the door opened, and Pyronica appeared. The pink demon appeared concerned. "Boss? Ya' ok?" She asked, looking at the triangle.

Cipher sighed, lowering himself back to his throne. "JUST DANDY, PYRA OL' PAL," he muttered, getting annoyed as he watched his minion walk in, sitting on the green velvet couch in front of Bill's throne.

"Listen, Bill Cipher, we all know this Fluvius Canatis thing is getting to your head." She shifted positions, crossing her legs. "How can ya' be sure it's gonna turn you into a...y'know, bag o' flesh?"

Bill chuckled at that. He admired the fact that the pink demon was using his slang. He sighed, again remembering his perils. "Man into monster, monster into man, just makes sense." The demon huffed. "Besides, I've seen it happen before myself. Then again of course I see everything."

Pyronica cackled wildly at Bill's joke, while the triangle sat in silence. That joke had reminded him of yet another power he would be losing. He sat there uncomfortably while his pink minion continued to laugh. Bill rolled his eyes. "CUT IT OUT, PINK," the demon hardened, silencing Pyronica.

She quickly stopped chortling, her flames shrinking as she quieted. Pyronica put her hands on her hips, pursing her lips. "Well, Cipher, you ruined my fun." The pink demon chuckled. "I'm fine boss."

"I WON'T EVEN HAVE CONTACT WITH YOU WHILE THE FLUVIUS HAS ME," Bill groaned, thinking of a factor he hadn't realized yet.

Pyronica chuckled. "Why don't I just ask one of the others to poof into your dreams? You weren't the only dream demon around here, y'know?"

But Bill was certainly the most powerful. Other dream demons could only stay in the mindscape for mere hours, while Bill could inhabit it for weeks, months even. "THOSE IDIOTS DON'T HAVE THE STRENGTH TO DO THAT."

The pink demon frowned. "How about me?"

Bill got off of his throne, hovering in mid-air. "OK PYRA HERE'S THE DEAL. FIRST OFF, I DON'T WANT ANYONE SPYING ON ME DURING MY LITTLE MEATSACK ADVENTURES. ONE, BECAUSE THAT'S MY JOB, AND TWO, YOU MIGHT SEE SOME THINGS YOU MIGHT NOT WANT TO," the demon sat beside his colleague, crossing his legs to mimic her. "IF YOU SEE ANYONE DOING ANYTHING INVOLVING ME, I WANT YOU TO SEND THEM DOWNSTAIRS. DOESN'T MATTER WHO THEY ARE OR WHEREVER THE HELL THEY CAME FROM."

Pyra nodded, looking at the triangle. "Alright boss." She looked at the door. "Speakin' of torture, what's takin' so long downstairs?"

Bill winced as he felt a strange tug in the lower half of his body. The transformation could be taking place very soon. Getting the imbeciles in the 'basement' to cooperate could be a task, but if it could at least postpone his fleshy fate he would be  
style="font-style: italic; font-size: 16pt;"less angry. Possibly. "I'LL CHECK ON IT. YOU DELIVER THAT, UH, MESSAGE TO EVERYBODY."

Bill watched as Pyronica sat up and strutted towards the door, opening it and closing it with a slam. The demon floated upwards, eye widening and arms flailing as his hover faltered, throwing him towards the ground. Bill's fists clenched. The transformation could be taking place in the next couple of hours and his stupid henchmaniacs still hadn't tortured the answers out of those ignorant beings who dared to not give Bill Cipher, being of pure energy what he wanted.

Oh, he would get what he desired.

He just had to do it himself.

The old elevator made its way to the lab, creaking noises echoing out. Dipper bit his lip anxiously, preparing to be scolded by Stanford once he reached the bottom floor. He put journal 3 under his shoulder, watching as the elevator neared Ford's lab, the very last floor of the house. Once it stopped, the boy watched as the elevator doors opened. Ford was standing in the middle of the lab, a welcoming smile on his face.

"Dipper! I thought it was you coming down here, my boy."

Dipper nodded awkwardly, stepping out of the elevator and flipping journal three to his desired page. "Uh, yeah. Actually, Great Uncle Ford, there's something I wanted to talk to you about."

The scientist in front of him took on a more serious demeanour, adjusting his tan trench coat slightly. "Yes? And what would that be?"

Quickly, Dipper flipped the book around in order to show his uncle the page about the Fluvius. "This river," Dipper explained. "I, uh, visited it a few days ago and may have accidentally fell into it," the boy explained, blushing slightly, embarrassed.

Stanford furrowed his brows, inspecting this page. "Hmm," he mumbled, in thought. "I never did get the chance to study this river in detail, Dipper." He bit his lip. "Has anything concerning happened since you fell into it?"

Dipper bit his lip, contemplating on telling the man right in front of him. He decided that it would be better in the long run to tell Stanford about his leg pains. "Well, for like, the past day or so my legs and head have been killing me. Also, according to Wendy I have a fever."

Ford put a hand to Dipper's forehead. "Yes, yes-you are indeed quite warm." He shifted slightly. "Have you ever experienced an illness that had these sort of symptoms before?" The man asked, kneeling in front of the boy.

"I dunno, the flu, maybe," Dipper explained, feeling drowsy. "But this doesn't really feel like it."

Ford put a hand on Dipper's shoulder, as he looked to be very dizzy. "What does it feel like then?" The scientist inquired.

Dipper blinked twice, registering his uncle's question. "Uh, it sort of feels like my whole body is having a migraine," the boy remarked.

Ford furrowed his brows, eying his nephew. "Stay down here tonight. If anything happens I will be awake to see and document it, all right Dipper?"


End file.
